CONICET | Buscador de Institutos y Recursos Humanos

Correlative studies in olive using data from different locations or years suggest that temperature canmodulate crop oil yield and oil composition. However, there are no published studies of manipulativeexperiments that demonstrate a direct role for temperature as a regulator of oil yield and oil qualityin olive. The objectives of this study were to: i) elucidate the effect of temperature during the fruitoil accumulation phase on fruit dry weight, oil concentration and fatty acid composition; and ii) identify the developmental window within the oil accumulation phase exhibiting the greatest sensitivity totemperature and that with the highest fruit capacity to recover from the temperature treatments. Twobranch-level experiments were conducted in a commercial orchard at Los Molinos (La Rioja, Argentina)using var. ?Arauco?. Both experiments were conducted during the oil accumulation phase by enclosing fruiting branches in transparent plastic chambers with individualized temperature control. The firstexperiment; known as the four month long experiment, employed four temperature treatments that wereapplied for a single period of four months: a control at ambient temperature, two heating levels (5◦C and10◦C warmer than the control), and a cooling level (5◦C cooler than the control). The second experimentconsisted of four separate successive one month long treatment periods, in each of which two temperature treatments were applied: control and heating (ca. 7◦C higher than control). In the four month longexperiment, fruit dry weight was not affected by average temperatures in the 16?25◦C range, but it wasreduced with further increases in temperature. Oil concentration decreased linearly at 1.1%◦C−1acrossthe whole range (16?32◦C) of average seasonal temperatures explored, while oleic acid concentrationdecreased 0.7%◦C−1over the same range. In the one month long experiment, 30 days of temperaturesca. 7◦C above ambient had a permanent negative effect on oil concentration at final harvest, particularlywhen the exposure to high temperature took place at the beginning of oil accumulation. By contrast,oleic acid concentration at the end of the treatment interval fell with increasing temperature but it couldrecover after treatment was removed in all periods except the first one. These results show that hightemperatures during the oil accumulation phase may negatively affect olive oil yield and quality in warmregions, particularly if the high-temperature event occurs early in the phase. Additionally, the response ofoleic acid concentration (%) to temperature under our experimental conditions was found to be oppositeto that of many annual oil-seed crops.